This invention concerns mold and core making machines involving the use of air pressure to blow a granular mold material, such as resin coated sand, from a supply into a pattern structure such as a flask or core box. The resin coated sand is cured to form a mold or core for use in casting metals. Such resin coated sand is quite free flowing such that it will tend to continue to flow out of a supply box even after the air pressure is cut off.
The continued flow forms "candles" on the molds or cores which must be removed prior to their use.
U.S. Pat. No. 3,530,928 issued on Sept. 29, 1970 for a "Blow Head Having Valve Means Cooperating with Flexible Chamber Walls" describes a valving for resin coated sand intended to control this tendency for sand flow.
U.S. Pat. No. 2,761,186 issued on Sept. 4, 1956 for a "Blow Tube for Core Blowing Machine" also is concerned with solving this same problem.
The arrangements shown in these patents do act to cut off flow after the blow tube is withdrawn from the pattern, but do not prevent the formation of features from flow within the bores in the pattern wall into which the blow tube is inserted.